It is known to hermetically seal an optoelectronic module within a metal housing to create an optoelectronic package which may be used, for example, in an optical communication system. Typically, an optoelectronic module includes a semiconductor laser diode mounted on a substrate, one or more lenses to focus the laser light generated by the laser, and one or more optical fibers to carry the focused laser light out of the package. The optical fiber(s) typically include a glass core for carrying the light which is protected by a coating of polymer. The polymer coating is stripped and the core or a section of the core is metallized (i.e., surrounded by solderable metal) to facilitate soldering the fiber in a desired location.
An example prior art housing 10 for an optoelectronic module is shown in FIG. 1. The housing 10 includes a body or can 12 which defines a chamber that is dimensioned to receive an optoelectronic module 14. In the example of FIG. 1, the housing 10 is adapted to receive a module having one optical fiber. To this end, the body 12 of the housing includes a fixed feedthrough 18. The feedthrough 18 is brazed to the metal can 12 such that it cannot be removed. In other words, the body 12 is constructed with the fixed feedthrough, 18 before the optoelectronic module 14 is placed in the chamber. An optoelectronic module 14 assembled outside the housing 10 is then inserted into the housing 10 by threading the optical fibers mounted to the module 14 through the fixed feedthrough 18 from within the chamber.
Another example prior art optoelectronic package 22 is shown in FIG. 2. The prior art package 22 of FIG. 2 includes a housing 24 which, like the housing 10 of FIG. 1 is adapted for use with an optoelectronic module 25. However, the module 22 is designed for use with two optical fibers 26, 28 which extend in opposite directions from one another.
To secure the fibers 26, 28 to the optoelectronic module 25, the outer polymer coating of a section of each of the fibers 26, 28 is stripped away and metallization is applied in the required section of the fiber. The metallized layer is then soldered to secure the fiber 26, 28 to the desired location of the optoelectronic module 25. While the metallized layer renders an optical fiber 26, 28 solderable, a metallized area of an optical fiber 26, 28 has reduced flexibility relative to the non-metallized, polymer coated portions of the fiber. As a result, the metallized areas of the optical fibers 26, 28 are more breakable than the non-metallized, polymer coated areas.
Because it is necessary to solder the optical fibers 26, 28 to or adjacent the optoelectronic module 25, the areas of the fibers 26, 28 adjacent the module 25 must be metallized. Since the area of the fiber that is stripped and metallized is much more fragile and susceptible to breakage under bend stresses, the housing 24 of FIG. 2 is extended. As a result, the assembled module 25 can be placed into the housing 24 and the fibers 26, 28 can be threaded through respective ones of first and second fixed feedthroughs 30, 32 (which are brazed on opposite ends of the housing 24) without severely bending the fibers. For example, fiber 26 may be threaded into its feedthrough 32. The module 25 may then be placed at the far end of the enclosure adjacent the enclosure wall. Then, the fiber 28 can be threaded into its feedthrough 30. Once the fibers 26, 28 are threaded, the module 25 must be centered within the enclosure to position the metallizations within their respective feedthroughs 30, 32 for final fiber sealing. The extended housing 24 ensures that sufficient distance exists between the ends of the fibers 26, 28 secured to the module 25 and the respective feedthroughs 30, 32 to eliminate the need to sharply bend the fibers 26, 28 when threading them through the feedthroughs 30, 32 thereby minimizing the bending of the fibers 26, 28 during assembly and, thus, reducing the risk of breakage.
As mentioned above, in addition to its extended length, the prior art housing 24 includes two fixed feedthroughs 30, 32. As shown in FIG. 2, each of the feedthroughs 30, 32 is a cylindrical structure having an end brazed to the body of the housing 24, and a central channel for receiving an optical fiber 26, 28. Each feedthrough 30, 32 also includes a solder holder 36 for receiving solder to hermetically seal the fiber to the housing 24. Each feedthrough 30, 32 also includes an epoxy holder 38 to receive epoxy to secure a furcation tube within the end of the feedthrough. The furcation tubes serve to protect their corresponding fibers 26, 28 against damage.